Fix Phase 0 compilation errors - validation fixes

Resolved 22 compilation errors:
- Fixed lib.rs re-exports to use correct submodule paths
- Added missing submodule declarations to module files
- Created stub files for referenced submodules
- Fixed main.rs imports to use lib.rs re-exports

Project now compiles successfully with only 2 expected warnings:
- dead_code warning for jobs field in JobManager
- unused_variable warning for job_manager in main

Both warnings are expected for scaffolding phase.

src/jobs/mod.rs

@@ -1,4 +1,4 @@
-//! Jobs Module - Async job queue and management
+//! Jobs Module - Async job queue management
 //!
 //! Handles job lifecycle management as defined in ARCHITECTURE.md:
 //! - Job queue and status tracking